Made with octagon at the base of the cylindrical section to enable really tight immersion heaters to be loosened by striking the handle.The one piece casting enables full transmission of power to the spanner unlike loose tommy bar types. Overall clearance around the spanner is 7/8in. (22mm) allowing easier fitting on insulated copper cylinders. A/F size 3 3/8in. 86mm. Buy MON361 from Amazon Marketplace. H71705 436171921 114963 114963 MON361